In general, a blood reservoir for temporarily storing blood from a body is used in an extracorporeal blood circulation circuit during cardiovascular surgery that involves extracorporeal blood circulation, in order to obtain a good operative field and allow surgical operations to be performed with ease. Minimally invasive surgery has garnered increased recognition in recent years, creating a need for an extracorporeal blood circulation system that is low-invasive with regard to the individual's body and blood.
Blood reservoirs in general can be divided broadly into open-type blood reservoirs, which have hard outer casings, and closed-type blood reservoirs, in which part of the outer casing surrounding the blood storage chamber is made from a flexible material. Open-type blood reservoirs are characterized by an excellent ability to remove air bubbles that are mixed in with the blood, and they allow the volume of the stored blood to be precisely ascertained. However, open-type blood reservoirs expose blood to the outside air and thus there is the risk of adverse effects on the blood, such as blood coagulation. On the other hand, closed-type blood reservoirs in principle do not expose blood to the outside air, and thus there are fewer untoward effects on the blood. However, some drawbacks to closed-type blood reservoirs include difficulty in gauging the volume of stored blood, and less ability to remove air bubbles than open-type blood reservoirs.
An example of a closed-type blood reservoir that has means for compensating for these deficiencies is disclosed in Patent Document 1. As shown in FIG. 23, the closed-type blood reservoir discussed in Patent Document 1 has a rotated oval space, for example, formed within a housing 111. A septum 103 made from a flexible material is disposed within the housing 111, and the septum 103 partitions the space into a blood storage chamber 101 and a volume adjustment chamber 102. The part of the housing 111 that covers the blood storage chamber 101 is provided with a blood inlet port 104 for introducing blood into the blood storage chamber 101 and a blood outlet port 105 for discharging the blood that has been introduced into the blood storage chamber 101 to outside the blood storage chamber 101. The part of the housing 111 that covers the volume adjustment chamber 102 is provided with a volume adjustment liquid port 108 for injecting and discharging a volume adjustment liquid.
The volume adjustment liquid is injected into and ejected from the volume adjustment chamber 102 by a pump or a pressure difference due to difference in height for example (not shown), through the volume adjustment liquid port 108. By driving a pump to change the amount of volume adjustment liquid that is stored by the volume adjustment chamber 102 and thereby move the septum 103, the volume of the volume adjustment chamber 102 and the volume of the blood storage chamber 101 can be changed. The volume of the volume adjustment chamber 102 can be ascertained by measuring the amount of volume adjustment liquid that is moved.
Patent Document 1: JP 2000-299 A